Chapter 8 Section 2 Chapter 8 Section 2 Review Page 196Review Page 196

Relative Age Dating

Absolute Age Dating

2. Explain why calculations 2. Explain why calculations of absolute age based on of absolute age based on

rates of erosion and rates of erosion and deposition can be inaccurate.deposition can be inaccurate.

The rate at which sediment is The rate at which sediment is deposited or eroded away can deposited or eroded away can vary from year to year due to vary from year to year due to many factors.many factors.

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3. Describe varves, and 3. Describe varves, and describe how and where they describe how and where they

form.form.

Varves are layers of sediment Varves are layers of sediment made of one layer of sand covered made of one layer of sand covered by one layer of silt. They are by one layer of silt. They are deposited at the bottom of glacial deposited at the bottom of glacial lakes and represent one year of lakes and represent one year of deposition.deposition.

VarvesVarves

44. Suppose you have a shark’s tooth . Suppose you have a shark’s tooth that you suspect is about 15,000 that you suspect is about 15,000

years old. Would you use years old. Would you use 238238U or U or 1414C C to date the tooth? Explain your to date the tooth? Explain your

answer.answer.

You would use radiocarbon (You would use radiocarbon (1414C) dating because the C) dating because the object is organic and because it is too young to be object is organic and because it is too young to be accurately dated by using accurately dated by using 238238U.U.

Radiocarbon Dating: Parent to Daughter

Chapter 8 Study NotesChapter 8 Study Notes

Section 2: Determining Absolute Section 2: Determining Absolute AgeAge

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The ______ age of an object is called The ______ age of an object is called _______ age._______ age. numericnumeric absoluteabsolute

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_______ age is the ______ age of an _______ age is the ______ age of an object.object. AbsoluteAbsolute numericnumeric

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_______ are banded _____ of sediment _______ are banded _____ of sediment deposited _________ in glacial lakes.deposited _________ in glacial lakes. VarvesVarves layerslayers annuallyannually

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A ______ is most like a tree ____.A ______ is most like a tree ____. varvevarve ringring

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Radioactive ____ is used to compare the Radioactive ____ is used to compare the absolute age of rocks because radioactive absolute age of rocks because radioactive decay happens at a relatively ______ rate.decay happens at a relatively ______ rate. decaydecay constantconstant

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________ dating is determining age ________ dating is determining age through _________ of isotopes.through _________ of isotopes. RadiometricRadiometric comparisoncomparison

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In __________ decay, parent isotopes are In __________ decay, parent isotopes are compared to __________ isotopes.compared to __________ isotopes. radioactiveradioactive daughterdaughter

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In ________ dating, scientists compare In ________ dating, scientists compare the proportion of a radioactive ______ the proportion of a radioactive ______ isotope to a stable _________ isotope.isotope to a stable _________ isotope. radiometricradiometric parentparent daughterdaughter

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A ________ is the time it takes for half of a A ________ is the time it takes for half of a sample of radioactive isotope to decay.sample of radioactive isotope to decay. half-lifehalf-life

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